Electric circuit breaker



Dec. 1, 1953 CASEY 2,661,414

ELECTRIC CIRCUIT BREAKER Filed March 9, 1951 2 Sheets-Sheet 1 Inventor R%ge1"b T Casey by H is AttoTWwey Dec. 1, 1953 R. T. CASEY ELECTRIC CIRCUIT BREAKER Filed March 9, 1951 2 Sheets-Sheet 2 INVENTOJ QJ ROBERT T. CASEY H IS ATTORNEY Patented Dec. 1, 1953 ELECTRIC CIRCUIT BREAKER Robert T. Casey, Bristol, Conn., assignor, by

mesne assignments, to General Electric Company, a corporation of New York Application March 9, 1951, Serial No. 214,769

9 Claims.

One object of the invention is to provide a small circuit breaker of simple but reliable construction.

Another object is to provide a circuit breaker which can be operated automatically or manually and when automatically tripped will return to a re-latched or normal off position.

Another object is to provide a manually and automatically operable circuit breaker which in case of an overload will operate to open a circuit automatically even if the manual actuator is held in the closed circuit position.

Another object is to provide a circuit breaker of simplified construction in which automatic opening is brought about by thermal and ma netic means mutually cooperating.

In the drawings,

Fig. l is a perspective view of a housing enclosing a circuit breaker embodying the form of the invention.

Fig. 2 is a side view of the circuit breaker mechanism showing the parts in the closed circuit position.

Fig. 3 is a similar view showing the parts of the circuit breaker in the manually-opened circuit position.

Fig. 4 is a transverse sectional view of the housing showing the interior mechanism, the section being taken on the plane of the line 44 of Fi 3.

Fig. 5 is a perspective view of the movable switch member and associated thermally controlled latch.

Fig. 6 is a view similar to that of Fig. 1 but showing the parts in the position they would occupy if the actuating lever is positively held in the closed circuit position during an automatic tripping action.

Fig. '7 is a transverse sectional view on the plane of the line l-'l of Fig. 3.

Fig. 8 is a fragmentary sectional view showing the latching rocker member interlocked with a section of the bimetal member.

Fig. 9 is an exploded perspective view of the parts of the hinged switch member together with the bimetal member and the rocker member.

Fig. 10 is a plan view showing the movable switch member and the associated bimetal memher.

The housing in the form shown consists of two separable parts I2, 12 formed of insulating material and held together by one or more screws or rivets or other fastening devices [3. The circuit terminals l4 and I5 may be of any suitable character. One of the switch contacts I6 is mounted on the terminal [5 and the other contact I! is carried by a metal switch arm member I8 which is hinged at l9. A main spring 20 seated in a recess in the base of the housing presses against the lug 21 which extends laterally from one edge of the switch arm IS. A conducting bimetal strip 22 has one end 23 bent at right angles and secured to a flange part 24 of the main switch arm (see Fig. 10). The other movable left-hand end of the bimetal is connected to the terminal I 4 by a flexible conductor 25.

The movable end of the switch member I8 is provided with a U-shaped yoke piece 26 which carries the movable contact l'l.

When the circuit is closed in the position of Fig. 2, the circuit through the circuit breaker may be traced from the terminal [4, through conductor 25, bimetal strip 22, lug 23, flange 24, yoke 26, contacts 11 and I 6 to terminal I5.

The rocker member 2'! has at one end a latch member 28 which normally rests on the upper edge of the bimetal strip 22 adjacent the movable left-hand end thereof. It will be observed that this end portion of the strip 22 constitutes a latch adjacent the pivoted end of the switch arm I8. The other end of the rocker arm 2'! is disposed between the side arms of yoke 26 and is guided by pivot projections 30, 30 slidable in slots 3|, 3|.

An auxiliary spring 32 is interposed between the base of the yoke 26 and one end of the rocker 21. The yoke 26 is provided with extension arms 33 which serve to guide the edges of the rocker arm 21. It will be observed that the pivotal projections 30 and spring 32 form a resilient pivotal connection for this end of the rocker arm.

The actuating lever 35 is pivoted at 36 between the opposite sides of the housing and extends through a slot in the top of the housing. The lever has an extension arm 3'! which is arranged to engage the rocker 27. It will be noted that this member 21 has an inclined central cam portion 38 with a shoulder 39 at one end of portion 38 and an extension or lug 40 which with the inclined portion 38 forms a socket for arm 31 in the open position.

In the normal closed circuit position of Fig. 2, the arm 31 of lever 35 engages over the top of the shoulder 39, in which position the lever is obstructed by a stop member 4| or the abutment 42 carried by the housing. In the open position shown in Fig. 3, the actuating lever 35 is stopped against a shoulder 42 in the housing. The lower arm 31 of the lever extends into the socket formed between the extension 40 and the incline 3B of the rocker. The rocker in this position is supported at one end by the bimetal strip 22 and at the other end by the spring 32.

An abutment 34 carried by the housing serves as a stop to limit the upward movement of the right hand end of rocker arm 21 in the open circuit position.

To close the circuit from the open or off position shown in Fig. 3, the lever 35 is moved to the left and the extension arm 3'! rides along the incline 38 and thus forces the rocker arm 21, switch arm member l8 and bimetal strip 22 from the open circuit position of Fig. 3 to the closed circuit position of Fig. 2.

The spring 32 is made relatively stronger than spring so that as the lever 35 initially moved to cause closing as described, the partially compressed spring 32 serves to transmit the closing force to spring 20 until the contacts l6 and I! meet. A small amount of further or continued travel of the lever 35 thereafter com presses spring 32 as shown in Fig. 2. This fur ther compression of spring 32 furnishes the necessary contact pressure.

It will be noted that instead of providing for contact pressure in this manner, I may provide for it by furnishing resilience in or resilient mounting of some other member. For instance,

instead of mounting the rocker arm 21 by means of projections in slots 3|, supported by spring 32, I may omit spring 32 and pivot the arm 2? in yolae 26 by means of supporting projections 3b in holes instead of in slots, and may provide for contact pressure by making the arm 2'! or resil ient material, or by providing a resilient mounting for one or both of contacts I6 and i! or by providing a resilient support for pivot it or for pivot 36 or in any other suitable manner.

It will be observed that regardless of how contact pressure is provided, latch 28 will be caused to press against bimetal 22 with a force which is considerably smaller than the contact pressure force. This reduction is brought about by the fact that arm 21 is supported at two points, i. e. approximately at each end, and furthermore the latch supporting point is substantially farther from the pressure-applying point of arm 3'1, than is the pivoting support point, at or adjacent to projections 30. Thus rocker arm 21 serves not only as a releasable latch to permit automatic opening, but also transmits a force at the releasing latch point which is only a small fraction of the switch-closing and contact force.

' In case of an excessive current passing through the bimetal member 22, the left hand end of the bimetal will warp away from the prongs 2'! of latch 28 carrying the upper edge of the bimetal out of engagement with the latch 28 thereby breaking the interlock between the rocker and bimetal strip. When this occurs, the main spring 20 presses the switch member 1% and bimetal strip 22 and yoke 26 upwardly carrying the contact H on" of the contact l6 and breaking the circuit, the parts assuming the position of Fig. 3, ready for closing, the same as after manual opening.

If, during the passage of excessive current, the actuating lever is manually restrained as shown in Fig. 6, the circuit nevertheless will be automatically opened as aforesaid. In this case, the'rocker member 21 pivots about the tip of actuator arm 31 to the position of Fig. 6. Upon release of such manual restraining force immediately thereafter, the continued bias of spring i 20 will move switch member l8 further open, to the position of Fig. 3, the rocker member 2'! meanwhile pivoting about abutment 34, moving the actuator 35 to the off position, and returning latch 28 above the upper edge of bimetal 22, to the relatched ofi position.

During such retracting movement, should the friction of the moving parts, and in particular the friction of latch 28 against the surface of bimetal 22 be such that the force of spring 20 is not great enough to return rocker member 21 to the full relatched position, the parts will stop in a condition approximately as shown in dotted lines in Fig. 6. Should this occur, it is only necessary to manually move actuator 35 to the full off position, during which action lower arm 31 will engage extension 40 and move the rocker member to the relatched or normal off position of Fig. 3.

If automatic tripping occurs at a time when the actuator 35 is not manually restrained, which will be the usual situation, the movement of the parts will be as follows. Release of the latch member 28 will permit the switch arm l8 to commence its upward movement, biased by spring 20. As this movement begins, rocker member 21 will pivot slightly about the tip of actuator arm 31. After pivoting through a small angle, however, the arm 21 will have its angle of contact with arm 31 altered so that it will cause the actuator 35 to move toward its off position. Thereafter, rocker arm 21 will pivot about projections fill in yoke 26 and then about abutment as so that the parts immediately return to the relatched or normal off position of Fig. 3.

In addition to warping due to thermal action, metal strip 22 is assisted in its bending action, to cause tripping, by magnetic action. Since the metallic switch arm l8 extends parallel to and closely spaced from metal strip 22, if it is paramagnetic an attraction is created between metal strip 22 and switch arm i8 due to the magnetic field surrounding metal strip 22 when it is conducting current. This force becomes appreciable at currents of short-circuit magnitude and opcrates to cause tripping of the mechanism on very high overloads. By employing bimetal in strip 22 with paramagnetic metal in switch arm E8 coop eration of thermal and magnetic tripping characteristics may be obtained.

I claim:

1. In a circuit breaker, a stationary contact, an elongated movable switch member pivotally mounted at one end and having a movable eontact at its opposite ends for cooperation with said fixed contact, a thermally deformable strip mounted at one end upon the movable end of said switch member and extending in substantially parallel relation with said switch member toward the pivotally mounted end thereof, an elongated rocker member pivotally mounted upon said movable end ofsaid switch member and extending in substantially parallel relation with said switch member toward said. pivotally mounted end there of, said rocker member normally engaging said deformable strip in latching relation adjacent the pivotally mounted end of said switch member thereby normally to maintain said rocker member and said switch member in relatively fixed positional relation and to permit rotation ofsaid rocker member relative to said switch member in response to thermal deformation of said strip, spring meansbiasing said switch member to a circuit opening position, and an actuating member having a portion engaging said rocker meber intermediate its ends to move said switch member to closed circuit position against the force of said spring means.

2. In a circuit breaker, a stationary contact, a switch arm pivoted at one end and having a contact at the opposite end for coacting with said stationary contact, a spring biasing said switch arm to an open circuit position, a bimetal strip secured at one end to the contact end of said switch arm and extending parallel to said switch arm, the free end of said bimetal strip being warpable transversely of the direction of movement of said switch arm, a rocker member pivotally and resiliently supported on the contact end of said switch arm and having a latch normally engaging said bimetal strip near its free end, said rocker member being normally held by said latch in substantially parallel relation with said switch and being rotatable with respect to said switch arm upon release of said latch, and a manually h operable lever engaging said rocker member inter mediate its ends in camming relation to move said switch arm to a closed circuit position against the biasing force of said spring, said rocker member being releasable upon the bending of said bimetal strip to provide for movement of said switch arm to said open circuit position by said spring.

3. In a circuit breaker, a housing, a stationary contact mounted in said housing, a switch member pivotally supported in said housing and having a movable contact for contacting with the stationary contact, a spring normally biasing the switch member toward open circuit position, a bimetal strip secured at one end to the movable end of said switch member and extending toward the pivotally mounted end of said switch member in substantially parallel relation therewith, said bimetal member being deformable in response to an excessive current through said contacts, an elongated rocker member slidably pivotally mounted at one end upon the movable end 01 said switch member and having at its opposite end a latch normally engaging said bimetal strip, and an actuating lever pivoted in the housing and having an inner extension engaging said rocker member intermediate its ends in camming relation to move said switch member to closed circuit position against the force of said spring.

4. In an electric circuit breaker, a switch member hinged at one end, a yoke carried by the other end of said switch member, a bimetal member secured at one end of said switch member and extending parallel to said switch member, a rocker member having a latch member at one end engaging said bimetal member, the other end of said rocker member being spring supported in said yoke, said rocker member having an inclined cam portion between the ends of said rocker member terminating in a shoulder, a pivoted operating member having an arm engaging said cam portion and the shoulder of said rocker member, and a spring coacting with said switch member to press the switch member and said rocker member toward said lever, said rocker member having a socket to receive the end of said operating lever so that the said lever may return said rocker member to interlocking relation with said bimetal member.

5. In an electric circuit breaker, an insulating housing, an elongated switch member pivotally supported at one end in said housing, a movable contact carried by the free end of said switch member, a bimetal strip fixedly supported on said switch member adjacent its free end and extending generally parallel to but spaced away from said switch member, spring means biasing said switch member to open circuit position, an elongated rocker member, one end of said rocker member being pivotally supported on said switch member adjacent its free end, the other end of said rocker member being releasably held by said bimetal adjacent its free end, manually operable means for applying contact closing force to said rocker member at a point intermediate its ends, and resilient means adapted to be stressed during contact closing movement of said manually operable means for furnishing contact pressure.

6. In an electric circuit breaker provided with a pair of terminals, a stationary contact connected to one of said terminals, an elongated switch member mounted on a fixed pivot at one end and carrying contact on its opposite movable end, a bimetal strip secured and electrically connected at one end to the movable end of said switch member and extending toward the pivot of said switch member in substantially parallel relation with said switch member, an electric connection between the opposite movable end of said bimetal strip and the other one of said terminals, an elongated rocker member extending along said switch member in substantially parallel relation, a resilient pivotal connection between one end of said rocker member and the movable end of said switch member, a latching portion on the opposite end of said rocker member normally engaging the movable end of said bimetal strip whereby said rocker member is held by said bimetal strip in a predetermined relation with said switch member, a pivoted actuating lever in engagement with said rocker member for moving the switch member to a closed circuit position with its contact in engagement with said stationary contact and for holding said switch member in said closed circuit position, said bimetal strip being adapted to warp when heated by an excesssive current passing through it thereby to release said rocker member for rotation relative to said switch member, and spring means for moving said switch member about its pivot to an open circuit position when said rocker member is released by said bimetal strip.

17. In an electric circuit breaker provided with a pair of terminals, a stationary contact connected to one of said terminals, an elongated switch member mounted on a fixed pivot at one end and carrying contact on its opposite movable end, a bimetal strip secured and electrically connected at one end to the movable end of said switch member and extending toward the pivot of said switch member in substantially parallel relation with said switch member, an electric connection between the opposite movable end of said bimetal strip and the other one of said terminals, an elongated rocker member extending along said switch member in substantially parallel relation, a resilient pivotal connection between one end of said rocker member and the movable end of said switch member, a latching portion on the opposite end of said rocker member normally engaging the movable end of said bimetal strip whereby said rocker member is held by said bimetal strip in a predetermined relation with said switch member, a pivoted actuating lever in engagement with said rocker member for moving the switch member to a closed circuit position with its contact in engagement with said stationary contact and for holding said switch member in said closed circuit position, said bimetal strip being adapted to warp when heated P7 by an excesssive current passing through it there- 'by to release said rocker member, spring means for moving said switch member about its pivot to an .open circuit position when said rocker member is released by said bimetal strip, and a lug on said rocker member in position to be engaged by said lever to return said rocker member to said predetermined relation with said switch member.

8. In an electric circuit breaker, a stationary contact, an elongated switch member mounted on a fixed pivot at one end and carrying a movable contact on its opposite movable end, a movable latch on said. switch member adjacent its pivoted end, an elongated rocker member extending along said switch member in substantially parallel relation, a pivotal connection between one end of said rocker member and the movable end of said switch member, a latching portion on the opposite end of said rocker member normally engaging said latch whereby said rocker member is held in fixed relative position with said switch member, a pivoted actuating lever in engagement with said rocker member for moving said switch member to a closed circuit position with said movable contact in engagement with said stationary contact and for normally holding said switch member in said closed circuit position, means responsive to the current through said contacts formoving said latch to release said rocker memher for rotation relative to said switch member, and spring means for moving said switch member about its pivot to an open circuit position when said-rocker member is released.

9. In an electric circuit breaker, a stationary contact, an elongated switch member mounted on a fixed pivot at one end and carrying a movable contact on its opposite movable end, a movone end of said rocker member and the movable end of said switch member, a latching portion on the opposite end of said rocker member normally engaging said latch whereby said rocker member is held in fixed relative position with said switch member, a cam portion on said rocker member intermediate its ends, a pivoted actuating lever in engagement with said cam portion for moving said switch member to a closed circuit position with said movable contact in engagement with said stationary contact and for normally holding said switch member in said closed circuit position, current responsive means connected in circuit with said contacts for moving said latch to release said rocker member for rotation relative to said switch member upon the occurrence of a predetermined excessive current in said contacts, and spring means for moving said switch member about its pivot to an open circuit position when said rocker member is released.

ROBERT T. CASEY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,130,368 Sachs Sept. 20, 1938 2203/1632 Frank June 4, 1940 2,229,842 Frank et al Jan. 28, 1941 2,233,187 Von Hoorn Feb. 25, 1941 2,254,067 Frank -i Aug. 26, 1941 2,320,355 Frank et al June 1, 1943 2,534,938 Woodward Dec. 19, 1950 

